Method of recovering sulphur from carbonyl sulphide



Patented Apr. 23, 1929.

PATENT. OFFICE.

UNITED STATES RAYMOND C. BENNER, OF NIAGARA FALLS, AND ALFRED PAULTHOMPSON, OF JACK- SON HEIGHTS, NEW YORK, ASSIGNORS TO GENERAL CHEMICALCOMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF RECOVERING S'ULI HUR FROM CARBONYL SULPHIDE.

No Drawing.

This invention relates to a method of puritying gases and more.especially to amethod of removing carbonyl sulphide from gases and therecovery of the sulphur therefrom in the elemental form. In many of theprocesses heretofore known and practised for the recovery of elementalsulphur from sulphur dioxide or directly from sulphide ores, seriousdiliiculties have been encountered and certain of the processes havebeen rendered commercially inoperata-ble on account of the loss ofsulphur in the form of carbonyl sulphide, or by the use of a largeamount of steam to effect the decomposition of this substance.

We have discovered that carbonyl sulphide may be readily decomposed andthe sulphur recovered therefrom in the elemental form by controlledoxidation thereof in the presence of activated bauxite. Moreparticularly' we have discovered that carbonyl sulphide may be readilyoxidized in the presence of activated bauxite and a small amount ofwater vapor, either at high or low tempera.- turcs, with air, oxygen,sulphur dioxide or other oxidizing gas.

When sulphur dioxide is passed through a bed of incandescentcarbonaceous fuel, the main products of the reduction are sulphur vapor,carbonyl sulphide, hydrogensulphide, carbon dioxide and water vapor.Likewise, when sulphide ore is treated with cabonaceou's fuel as, forexample, in the Hall process, considerable amounts of carbonyl sulphideand hydrogen sulphide are evolved, as well as elemental sulphur. Therelative proportions of carbonyl sulphide and hydrogen sulphide formedin either case will depend chiefly upon the quantity of water vapornormally present .in the process and the quantity of water that may beadded as steam. The effect of water is to increase the hydrogen sulphide:mddecreasc the carbonyl sulphide, as

carbonyl sulphide is quantitatively dccom' posed by steam, according totheequatlon H,() COS CO +H,S

In many of the older processes, it has been considered necessary todecompose carbonyl sulphide into hydrogen sulphide by the addition ofsteam, and then to add a limited amount of air or sulphur dioxide to thehydrogen sulphide thus for-med to produce elemental sulphur and water.Any of these catalytic activity for long periods.

Application filed January 21, 1927. Serial No. 165,571.

methods are rendered economically difficult, not only by the addedexpense of using steam, but also by the incomplete conversion of thehydrogen sulphide to elemental sulphur, in accordance with thereversible equation caused by the presence of the large amount of watervapor.

According to our invention, the gaseous products from the treatment ofsulphur dioxideor sulphide ore with carbonaceous fuel, or the gases fromany other source which contain carbonyl sulphide (and which may alsocontain hydrogen sulphide) are mixed with at least sufiicient oxidizinggas, i. 0., air, oxygen, sulphur dioxide, etc., to completely oxidizethe carbonyl sulphide (and hydrogen sulphide) to elemental sulphur an dthe mixed gases contacted with activated bauxite at an elevatedtemperature. When the mixed gases are thus treated at comparatively hightemperatures, say 300 to 700 C. practically no water vapor or itsconstituents are required to promote the oxidation. In any event, anamount of moisture equivalent to the normal humidity of the atmospherewill be found suflicient and no additional water vapor or steam will berequired. The reactions occur according to the equations The gasmixture, leaving the activated bauxite catalyst, is cooled to condensethe elemental sulphur produced and the sulphur is collected by anysuitable means.

Bauxitcs of varying analysesmay be employed to catalyze these reactions.In general we have found that those bauxites high in combined water,such as British Guiana and Oolitic bauxites are particularly active incatalyzing these reactions and retain their However, Dalmatian bauxite,which contains only a moderate amount of combined water,

has been found quite satisfactory. The bauxite is activated by slowlyheating the natural mineral in granular or lump form to about 400 to 500C., the temperature being maintained for several hours to causesubstantial dehydration. The dehydration may be accomplished in vacuo,if desired.

Gases containing carbonyl sulphide may likewise be purified from thissubstance by the oxidation thereof with air, oxygen or sulphur dioxideat comparatively low temperatures, i. e., below 300 C. and the. sulphurrecovered in the elemental form. This process is particularlyadvantageous in removing small amounts and even up to 5% of carbonylsulphide. In the treatmentof a gas to oxidize the carbonyl sulphide atcomparatively low temperatures, we have found, however, that smallamounts of water vapor are required, the water apparently serving as acatalytic agent or carrier for the oxidation reaction.

For example, air is added to a gas containing one to two percentcarbonyl sulphide by volume in such proportions as to provide at leastsuflicient oxygen to oxidize the carbonyl sulphide to carbon dioxide andsulphur. Preferably an excess of air will be employed to insure acomplete oxidation. If the gas mixture is substantially free from watervapor or from substances which will form water vapor upon oxidation withthe oxidizing gas present, a small amount of moisture is added toprovide about 2.5% by volume of water vapor. Where, however, the gasmixture contains sufficient moisture none need be added. This gasmixture, when passed through a layer of activated bauxite at about 200C. will be entirely freed from the carbonyl sulphide by the oxidationthereof with the oxygen. The reactions may occur according to thefollowing equations:

It will be noted that the water employed in the first reaction isre-formed in the second reaction, so that the combined reaction may bedefined as carried on at temperatures below 200 C. but

this operation is notpreferred because of the lower reaction speed, andconsequently,

greater proportion of catalyst required. The

by the application of heat or suitable solvents. The process may becarriedout at ordinary or raised pressures, and various othermodifications may be made without departing from the spirit of theinvention.

We claim:

1. The process of producing elemental sulphur from gases containingcarbonyl sulphide which comprises contacting a mixture of said gas andan oxidizing gas with activated bauxite.

2. The process of producing elemental sulphur from gases containingcarbonyl sulphide which comprises contacting a mixture of said gas andsulphur dioxide with activated bauxite.

3. The process of removing carbonyl sulphide from gases which consistsin contactin; said gases with activated bauxite in the presence of anoxidizing gas and water vapor.

4. The process of removing carbonyl sulphide from gases which consistsin contacting said gases with activated bauxite in the presence of anoxidizing gas and a small amount of water vapor and maintaining atemperature below 300 C.

5. The process of removing carbonyl sulphide from gases which consistsin catalytically oxidizing carbonyl sulphide with sulphur dioxide in thepresence of a small amount of water vapor at a temperature below 300 C.V

In testimony whereof, we aflix our signatures.

RAYMOND C. BENNER. ALFRED PAUL THOMPSON.

CERTIFICATE OF CORRECTION.

Patent No. 1,710,141. Granted. April 23,- 1929, to

RAYMOND C. BENNER ET AL.

Ito is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1,lines 32 and 33,

for the misspelled word "cabonaceous" read "carbonaceous"; page 2, line45, for the word "Sulphide" read "Sulphur"; and that the said LettersPatent should be read with these corrections therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this 28th day of May, A. D. 1929.

M. J. Moore,

'(Seall Acting Commissioner of Patents.

CERTHFHGATE 0F (IQRRECTWN. Patent No. 1,710,141. Apt-it 23, 1929, toRAYMGND G. EENNER ET AL It is hereby certified that ettsr appears in themintedspeeitieatien of the above numbered patent requiring een'eetisn asfefltews: Page 1, lines 32 and 33, for the misspelled Word *eshenaeeeus"read "cm-tmneeeeus"; page 2, line 45, for the Word "Sulphids" read"Sttiphur"; and that Lettees Patent should be read with theseeerreetiens their-stain that the same may eontsrm "t0 the reesrd 0f thecase in the Patent Offieev Signed and seated this 28th stay of May, A. D5929.

M. 5. ltttoere (Seal) Acting Csmmissiener of Patents.

